1. Field of the Invention
The present invention relates to a technique for controlling the operation of a pump, including providing a method of controlling the operation of a pump at a constant pressure using motor current as a sensing parameter and motor voltage as a controlling parameter.
More particularly, the present invention relates to a method and apparatus using a pump control to keep an outlet pressure constant based at least partly on sensing motor current and a unique algorithm of tracking the V-I characteristics of a pump.
2. Brief Description of Related Art
Many pumps known in the art include a mechanical pressure switch, or semiconductor hall sensors, or load cells, or any other type of electronic pressure sensing device, that shuts off the pump when certain pressure (i.e., the shut-off pressure) is exceeded. The pressure switch, hall sensor or load cell is typically positioned in physical communication with the fluid in the pump. When the pressure of the fluid exceeds the shut-off pressure, the force of the fluid moves the mechanical switch to open the pump's power circuit or generates corresponding electrical signal to trace the set pressure. Mechanical switches have several limitations. For example, during the repeated opening and closing of the pump's power circuit, arcing and scorching often occurs between the contacts of the switch. The pressure cannot remain constant because of the non-repetitive and/or non-linear behavior. So relying totally on the pressure switch or sensor will always give an inconsistence control loop.
In view of this, there is a need in the art for an improved pump controller that solves the problems related to the mechanical pressure switches or sensors in the known pump designs.